Methods and Apparatus for Efficiently Accessing Reduced Color-Resolution Image Data

1. A method for storing image data for efficient data access, the image data for display in an original or other orientation, comprising: selecting a storage arrangement, the selected storage arrangement corresponding with a particular display orientation; receiving the image data as luma and chroma samples, the image data having been created by chroma-subsampling an image in the original orientation using 2×2 pixel tiles as sample areas; providing a memory, the memory having a plurality of first memory portions and a plurality of second memory portions, each of the first and second memory portions sized to store four samples and accessible at a distinct memory address; generating a first memory address according to the selected storage arrangement for each 2×2 pixel tile of the image, and storing the luma samples in the memory, the storing of the luma samples including storing the luma samples of a particular pixel tile together in a first memory portion having the first memory address generated for the particular pixel tile; and generating a second memory address according to the selected storage arrangement for each pair of adjacent 2×2 pixel tiles of the image, and storing the chroma samples in the memory, the storing of the chroma samples including storing the chroma samples of a particular pair of adjacent pixel tiles together in a second memory portion having the second memory address generated for the particular pair of adjacent pixel tiles.

2. The method of claim 1 , wherein the storing of the luma samples of a particular pixel tile together in a first memory portion having the first memory address generated for the particular pixel tile includes storing the luma samples in a particular order, the particular order including: arranging the luma samples of top and bottom horizontal lines of the particular pixel tile in a raster sequence beginning with the top-left pixel, wherein the first and second horizontal lines are determined according to a view of the pixel tile in the particular display orientation.

3. The method of claim 1 , wherein the storing of the chroma samples of a particular pair of adjacent pixel tiles together in a second memory portion having the second memory address generated for the particular pair of adjacent pixel tiles includes storing the chroma samples in a particular order, the particular order including: arranging the chroma samples of a left pixel tile and a right pixel tile in a sequence in which the chroma samples of the right pixel tile follow the left pixel tile, the right pixel tile being horizontally adjacent to the left pixel tile, wherein horizontal adjacency is determined according to a view of the image in the particular display orientation.

4. The method of claim 1 , wherein the generating of a first memory address according to the selected storage arrangement for each pixel tile of the image includes generating sequential first memory addresses for horizontally-adjacent pixel tiles, wherein horizontal adjacency is determined according to a view of the image in the particular display orientation.

5. The method of claim 1 , wherein the generating of a second address according to the selected storage arrangement for each pair of adjacent pixel tiles of the image includes generating sequential second memory addresses for horizontally-adjacent pairs of pixel tiles, wherein horizontal adjacency is determined according to a view of the image in the particular display orientation.

6. The method of claim 1 , wherein the image data having been created by chroma-subsampling an image in the original orientation using 2×2 pixel tiles as sample areas includes chroma-subsampling the image in a 4:2:0 format.

7. The method of claim 1 , wherein the image data having been created by chroma-subsampling an image in the original orientation using 2×2 pixel tiles as sample areas includes chroma-subsampling the image in a 4:1:1 format.

8. The method of claim 1 , wherein two or more chroma components of a pixel tile are averaged to create a chroma sample.

9. The method of claim 1 , further comprising fetching the image data from the memory for display in the particular display orientation, the fetching of image data including fetching the luma samples of a first line of the image from a first set of memory addresses, and thereafter fetching the luma samples of a second line of the image from the first set of memory addresses, wherein the luma samples of the first and second lines are fetched from sequential addresses of the first set of memory addresses.

10. The method of claim 1 , further comprising fetching the image data from the memory for display in a second display orientation, the second display orientation being different from the particular display orientation, the fetching of image data including fetching the luma samples of a first line of the image from a first set of memory addresses, and thereafter fetching the luma samples of a second line of the image from the first set of memory addresses, wherein the luma samples of the first and second lines are fetched from addresses of the first set of memory addresses in a particular order, the particular order being in accord with the second display orientation.

11. The method of claim 1 , the generating of a unique second memory address according to the selected storage arrangement for each pair of adjacent pixel tiles of the image further including: generating of a unique second memory address according to the selected storage arrangement for each pair of horizontally-adjacent pixel tiles of the image, wherein horizontal adjacency is determined according to a view of the image in the particular display orientation.

12. The method of claim 1 , the generating of a unique second memory address according to the selected storage arrangement for each pair of adjacent pixel tiles of the image further including: generating of a unique second memory address according to the selected storage arrangement for each pair of vertically-adjacent pixel tiles of the image, wherein vertically adjacency is determined according to a view of the image in the particular display orientation.

13. A display controller for storing image data of an image for efficient data access, the image data for display in an original or other orientation, comprising: a memory, the memory having a plurality of first memory portions and a plurality of second memory portions, each of the first and second memory portions sized to store four pixel components and accessible at a distinct memory address; a unit to receive the image data and to store the received image data in the memory, wherein the unit stores image data including pixels haying one luma component for each pixel of the image and stores two chroma components for each 2×2 pixel tile of the image; and an address generator to generate: a first memory address for each 2×2 pixel tile of the image according to a selected storage arrangement corresponding with a particular display orientation, wherein the unit stores the luma components of a particular pixel tile together in a first memory portion having the first memory address generated for the particular pixel tile; and a second memory address for each pair of adjacent 2×2 pixel tiles of the image according to the selected storage arrangement, wherein the unit stores the chroma components of a particular pair of adjacent pixel tiles together in a second memory portion having the second memory address generated for the particular pair of adjacent pixel tiles.

14. The display controller of claim 13 , wherein the unit stores the luma components of a particular pixel tile together in a first memory portion having the first memory address generated for the particular pixel tile in a particular order, the particular order including: arranging the luma components of top and bottom horizontal lines of the pixel tile in a raster sequence beginning with the top-left pixel, wherein the top and bottom horizontal lines are determined according to a view of the pixel tile in the particular display orientation.

15. The display controller of claim 13 , wherein the unit storing the chroma components of a particular pair of adjacent pixel tiles together in a second memory portion having the second memory address generated for the particular pair of adjacent pixel tiles further comprises the unit storing the chroma samples in a particular order, the particular order including: arranging the chroma components of a left pixel tile and a right pixel tile in a sequence in which the chroma samples of the right pixel tile follow the left pixel tile, the right pixel tile being horizontally adjacent to the left pixel tile, wherein horizontal adjacency is determined according to a view of the image in the particular display orientation.

16. The display controller of claim 13 , wherein the address generator generating a first memory address for each 2×2 pixel tile of the image according to a selected storage arrangement corresponding with a particular display orientation further comprises the address generator generating sequential first memory addresses for horizontally-adjacent pixel tiles, wherein horizontal adjacency is determined according to a view of the image in the particular display orientation.

17. The display controller of claim 13 , wherein the address generator generating a second address according to the selected storage arrangement for each pair of adjacent pixel tiles of the image further comprises the address generator generating sequential second memory addresses for horizontally-adjacent pairs of pixel tiles, wherein horizontal adjacency is determined according to a view of the image in the particular display orientation.

18. The display controller of claim 13 , wherein the unit receives image data that has been chroma-subsampled in a 4:2:0 format.

19. The display controller of claim 13 , wherein the unit is operable to chroma-subsample received image data according to a 4:2:0 format.

20. The display controller of claim 19 , wherein the unit receives the image data as raster ordered pixels.

21. The display controller of claim 13 , wherein the unit receives image data that has been chroma-subsampled in a 4:1:1 format.

22. The display controller of claim 13 , wherein the unit is operable to chroma-subsample received image data according to a 4:1:1 format.

23. The display controller of claim 13 , wherein two or more chroma components of a pixel tile are averaged to create a chroma sample.

24. A display controller, comprising: a memory array, the memory array having a plurality of rows each row sized to store four pixel components and accessible at a distinct memory address; a unit to receive pixel data of an image in raster order, and to store one luminance component for each pixel of the image and two chrominance components for each 2×2 pixel tile of the image in the memory array; and an address generator to generate: a first memory address for each 2×2 pixel tile of the image, and a second memory address for each pair of adjacent 2×2 pixel tiles of the image; wherein the unit stores the luminance components of a particular pixel tile at the first memory address generated for the particular pixel tile, and the unit stores the chrominance components of a particular pair of adjacent pixel tiles at the second memory address generated for the particular pair of pixel tiles.

25. The display controller of claim 24 , wherein the address generator generating a first memory address for each pixel tile of the image further comprises the address generator generating sequential first memory addresses for horizontally-adjacent pixel tiles, wherein horizontal adjacency is determined according to a view of the image in a first orientation.

26. The display controller of claim 25 , wherein the address generator generating a first memory address for each pixel tile of the image further comprises the address generator generating sequential first memory addresses for horizontally-adjacent pixel tiles, wherein horizontal adjacency is determined according to a view of the image in a second orientation, the second orientation being a ninety-degree, left-rotated view of the image in the first orientation.

27. The display controller of claim 24 , wherein: the memory array includes a first memory array and a second memory array, each generated first memory address identifies a row of the first memory array, and each generated second memory address identifies a row of the second memory array.

28. The display controller of claim 24 , the address generator including an address counter, wherein the address counter generates a first memory address for each pixel tile of the image, and a second memory address for each pair of adjacent pixel tiles of the image, the second memory address being the left N-1 bits of the first memory address, where the first memory address is N bits.

29. The display controller of claim 24 , wherein the two chrominance components for each 2×2 pixel tile of the image include a Cr component and a Cb component.

30. The display controller of claim 24 , wherein the two chrominance components for each 2×2 pixel tile of the image include an I component and a Q component.

31. A non-transitory computer readable medium embodying a program of instructions for execution by a computer which, when executed by the computer, carries out a method for storing image data for efficient data access, the image data for display in an original or other orientation, comprising: receiving an indication of a selected storage arrangement corresponding with a particular display orientation; receiving the image data as luma and chroma samples, the image data having been created by chroma-subsampling an image in the original orientation using 2×2 pixel tiles as sample areas; generating a first memory address for a memory according to the selected storage arrangement for each 2×2 pixel tile of the image, the memory having a plurality of first memory portions and a plurality of second memory portions, each of the first and second memory portions sized to store four samples and accessible at a distinct memory address, and storing the luma samples in the memory, the storing of the luma samples including storing the luma samples of a particular pixel tile together in a first memory portion having the first memory address generated for the particular pixel tile; and generating a second memory address for the memory according to the selected storage arrangement for each pair of adjacent 2×2 pixel tiles of the image, and storing the chroma samples in the memory, the storing of the chroma samples including storing the chroma samples of a particular pair of adjacent pixel tiles together in a second memory portion having the second memory address generated for the particular pair of adjacent pixel tiles.